Inorganic Aerosol Chemistry Data

The files Nauru99_submicron_ic.csv and Nauru99_supermicron_ic.csv contain the sub- and supermicron inorganic ion concentrations, respectively, collected near the island of Nauru during the Nauru99 cruise. The samples were taken with two-stage multi-jet cascade impactors [Berner et al., 1979] sampling air at 55% RH. The 50% aerodynamic cutoff diameters, D50(aero), were 1.1 and 10 µm. Based on these sizes, submicron refers to particles with D(aero) < 1.1 µm and supermicron refers to particles with 1.1 µm < D(aero) < 10 µm at 55% RH.

The impaction stage at the inlet of the impactor was coated with silicone grease to prevent the bounce of larger particles onto the downstream stages. Tedlar films were used as the collection substrate in the impaction stage and a Millipore Fluoropore filter (1.0-µm pore size) was used for the backup filter. Films were cleaned in an ultrasonic bath in 10% H2O2 for 30 min, rinsed in distilled, deionized water, and dried in an NH3- and SO2-free glove box. Filters and films were wetted with 1 mL of spectral grade methanol. An additional 5 mLs of distilled deionized water were added to the solution and the substrates were extracted by sonicating for 30 min. The extracts were analyzed by ion chromatography [Quinn et al., 1998]. All handling of the substrates was done in the glove box. Blank levels were determined by loading an impactor with substrates but not drawing any air through it.

All times are in units of fractional DOY (i.e., DOY 060.5000 = 12 noon on March 1).